Hi,
in the Savage driver I will have to pass vertex data to the kernel. On
Savage3D/IX/MX I have worked out how to do real vertex DMA, so this is
no problem. On Savage4 the vertex DMA engine can't cope with all vertex
formats, so I need to used drawing commands with inline vertex data
sometimes. So I see two choices for how to get the vertex data from user
space to the kernel:
* shared memory buffers created by the Xserver
advantages:
* as long as I don't use command DMA it avoids one extra
copy
disadvantages:
* limited number of buffers
* static allocation at xserver startup
* copy from user
advantages:
* dynamic memory allocation (at client startup)
disadvantages:
* extra copy if I don't use command DMA (need to use
memcpy_mmio which doesn't exist as copy_from_user)
Since I'm going to implement command DMA on Savage4 eventually, I'd
prefer the "copy from user" method. However, I remember reading about
64-bit issues with user pointers in data structures passed between
kernel and user-space. Is there any 64-bit clean way of copying a vertex
buffer from user-space. I guess the only way would be to pass the
pointer directly as ioctl argument. Then all extra information (like
vertex format and number of vertices) would have to be in a header of
that vertex buffer. Am I on the right track so far?
Thanks,
Felix
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| Felix Kühling <[EMAIL PROTECTED]> http://fxk.de.vu |
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